#region CPL License
/*
Nuclex Framework
Copyright (C) 2002-2019 Nuclex Development Labs

This library is free software; you can redistribute it and/or
modify it under the terms of the IBM Common Public License as
published by the IBM Corporation; either version 1.0 of the
License, or (at your option) any later version.

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
IBM Common Public License for more details.

You should have received a copy of the IBM Common Public
License along with this library
*/
#endregion

using System;
using System.Windows.Forms;

namespace Nuclex.Windows.Forms.Messages {

  /// <summary>Uses task dialogs to display message boxes</summary>
  public class StandardMessageBoxManager : IMessageService {

    #region class MessageScope

    /// <summary>Triggers the message displayed and acknowledged events</summary>
    private class MessageScope : IDisposable {

      /// <summary>
      ///   Initializes a new message scope, triggering the message displayed event
      /// </summary>
      /// <param name="self">Message service the scope belongs to</param>
      /// <param name="image">Image of the message being displayed</param>
      /// <param name="text">Text contained in the message being displayed</param>
      public MessageScope(
        StandardMessageBoxManager self, MessageBoxIcon image, MessageText text
      ) {
        EventHandler<MessageEventArgs> messageDisplayed = self.MessageDisplaying;
        if(messageDisplayed != null) {
          messageDisplayed(this, new MessageEventArgs(image, text));
        }

        this.self = self;
      }

      /// <summary>Triggers the message acknowledged event</summary>
      public void Dispose() {
        EventHandler messageAcknowledged = self.MessageAcknowledged;
        if(messageAcknowledged != null) {
          messageAcknowledged(this, EventArgs.Empty);
        }
      }

      /// <summary>Message service the scope belongs to</summary>
      private StandardMessageBoxManager self;

    }

    #endregion // class MessageScope

    /// <summary>Delegate for the standard message box show function</summary>
    /// <param name="owner">Window that will modally display the message box</param>
    /// <param name="text">Text that will be presented to the user</param>
    /// <param name="caption">Contents of the message box' title bar</param>
    /// <param name="buttons">Buttons available for the user to choose from</param>
    /// <param name="icon">Icon that will be displayed next to the text</param>
    /// <returns>The choice made by the user if multiple buttons were provided</returns>
    private delegate DialogResult ShowMessageBoxDelegate(
      IWin32Window owner,
      string text,
      string caption,
      MessageBoxButtons buttons,
      MessageBoxIcon icon
    );

    /// <summary>Triggered when a message is displayed to the user</summary>
    public event EventHandler<MessageEventArgs> MessageDisplaying;

    /// <summary>Triggered when the user has acknowledged the current message</summary>
    public event EventHandler MessageAcknowledged;

    /// <summary>Initializes a new task dialog message service</summary>
    public StandardMessageBoxManager() : this(NullActiveWindowTracker.Default) { }

    /// <summary>Initializes a new task dialog message service</summary>
    /// <param name="tracker">
    ///   Active window tracker used to obtain the parent window for message boxes
    /// </param>
    public StandardMessageBoxManager(IActiveWindowTracker tracker) {
      this.tracker = tracker;
      this.showMessageDelegate = new ShowMessageBoxDelegate(MessageBox.Show);
    }

    /// <summary>Asks the user a question that can be answered via several buttons</summary>
    /// <param name="image">Image that will be shown on the message box</param>
    /// <param name="text">Text that will be shown to the user</param>
    /// <param name="buttons">Buttons available for the user to click on</param>
    /// <returns>The button the user has clicked on</returns>
    public DialogResult ShowQuestion(
      MessageBoxIcon image, MessageText text, MessageBoxButtons buttons
    ) {
      using(var scope = new MessageScope(this, image, text)) {
        return showMessageBoxInActiveUiThread(
          text.Message,
          text.Caption,
          buttons,
          image
        );
      }
    }

    /// <summary>Displays a notification to the user</summary>
    /// <param name="image">Image that will be shown on the message bx</param>
    /// <param name="text">Text that will be shown to the user</param>
    public void ShowNotification(MessageBoxIcon image, MessageText text) {
      using(var scope = new MessageScope(this, image, text)) {
        showMessageBoxInActiveUiThread(
          text.Message,
          text.Caption,
          MessageBoxButtons.OK,
          image
        );
      }
    }

    /// <summary>Displays the message box in the active view's thread</summary>
    /// <param name="message">Text that will be presented to the user</param>
    /// <param name="caption">Contents of the message box' title bar</param>
    /// <param name="buttons">Buttons available for the user to choose from</param>
    /// <param name="image">Image that will be displayed next to the text</param>
    /// <returns></returns>
    private DialogResult showMessageBoxInActiveUiThread(
      string message,
      string caption,
      MessageBoxButtons buttons,
      MessageBoxIcon image
    ) {
      Form mainWindow = this.tracker.ActiveWindow;
      if(mainWindow != null) {
        return (DialogResult)mainWindow.Invoke(
          this.showMessageDelegate,
          (IWin32Window)mainWindow, message, caption, buttons, image
        );
      }

      // No window tracker or unknown main window -- just show the message box
      return MessageBox.Show(message, caption, buttons, image);
    }

    /// <summary>Provides the currently active top-level window</summary>
    private IActiveWindowTracker tracker;
    /// <summary>Delegate for the MessageBox.Show() method</summary>
    private ShowMessageBoxDelegate showMessageDelegate;

  }

} // namespace Nuclex.Windows.Forms.Messages